(368h) Differences in the Dynamics of Cylindrical and Spherical Particles in a Rotating Drum Using Multiple Radioactive Particle Tracking

Differences in the Dynamics
of Cylindrical and Spherical Particles in a Rotating Drum Using Multiple
Radioactive Particle Tracking

Majid Rasouli, François Bertrand*, Jamal
Chaouki*

Department
of Chemical Engineering, École Polytechnique de Montréal, P. O. Box 6079, Succ.
Centre-ville, Montréal, QC, Canada, H3C 3A7, jamal.chaouki@polymtl.ca,
francois.bertrand@polymtl.ca

Rotating
drums are widely used to process granular materials in the chemical, pharmaceutical,
food-processing, polymer, and waste treatment industries, among others, for
applications such as mixing, size reduction, sintering, coating, heating,
cooling, drying, and chemical reactions. This broad array of applications is
made possible by the ability of rotating drums to handle heterogeneous
feedstock and to ensure satisfactory mixing and heat transfer of the solid
phase¹. Since the flow dynamics
of particles determines to a great extent the mass and heat transfer rates, it
plays a critical role in controlling and/or limiting the processes mentioned above². The optimal design
and operation of rotating drums require in-depth fundamental knowledge of the
phenomena that occur inside them, including the transverse flow that controls
primary effects such radial particle movement and particle mixing and/or
segregation, as well as secondary effects such as bed temperature, reaction
rates, and the rate of axial particle movement.

The
flow behavior of spherical particles has been often studied. However, investigations
of cylindrical particles, which are not numerous in the literature,  are required
since these particles have many uses (biomass pellets, capsules, rice, candy,
etc.) and, more importantly, since their shape is known to affect their flow
behavior³ in terms of shear resistance,
dilation under shear, compaction efficiency, transfer of momentum between
translational and rotational movements, and their ability to form arches and
block the flow⁴.

The
goal of the present study was to compare the flow behavior of spherical and
cylindrical particles in a rotating drum. We used the RPT technique to
determine the positions of the spherical particles over time. We used the MRPT
technique⁵ to track the positions
and orientations of the cylindrical particles and calculate the components of
their transverse flow dynamics in the rotating drum. To illustrate, Fig. 1
shows velocity vectors of the transverse flow of spherical and cylindrical
particles at the same rotational speed (10 RPM) in the rotating drum.

Figure 1:
Velocity vectors for (a)
spherical and (b) cylindrical particles at a rotational speed of 10 RPM⁶

Literature
cited

1.         Dube O, Alizadeh E, Chaouki J, Bertrand F. Dynamics of non-spherical
particles in a rotating drum. Chemical Engineering Science. Sep 20
2013;101:486-502.

2.         Mellmann
J, Specht E, Liu X. Prediction of rolling bed motion in rotating cylinders. AIChE
Journal. 2004;50(11):2783-2793.

3.         Ridgway
K, Rupp R. Mixing of powder layers on a chute. The effect of particle size and
shape. Powder Technology. 1971;4(4):195-202.

4.         Cleary
PW. DEM prediction of industrial and geophysical particle flows. Particuology.
2010;8(2):106-118.

5.         Rasouli
M, Bertrand F, Chaouki J. A multiple radioactive particle tracking technique to
investigate particulate flows. AIChE Journal. 2015;61(2):384-394.

6.         Rasouli
M, Dubé O, Bertrand F, Chaouki J. Investigating the dynamics of cylindrical
particles in a rotating drum using multiple radioactive particle tracking. AIChE
Journal. 2016.

Acknowledgments

This work was made possible by financial support from
Praxair and the Natural Sciences and Engineering Research Council of Canada
(NSERC). The authors are grateful to Cornelia Chilian and Cristina Cimpan
(Institute of Nuclear Engineering) for activating the tracers, Sepehr
Hamzelouia for helping to measure the static repose angle, and Amin Esmaeili
for helping to determine the positions of the RPT detectors.